1. Technical Field
The embodiments herein generally relate to medical devices, and, more particularly, to a modular lateral expansion device used during orthopedic surgeries.
2. Description of the Related Art
In lumbar interbody spinal fusion procedures, two adjacent vertebral bodies are fused together by entirely or partially removing the degenerated intervertebral disc between two adjacent vertebrae and inserting an implant within the vertebral body. Lastly, fusion material (e.g., bone graft) may be placed within the vertebral body which along with the body's natural cells promotes bone formation.
The greatest compressive strength in the spine lies within the outer 30% of the vertebral bodies. Due to variable soft tissue anatomy, it is often difficult surgically to seat intervertebral body devices sufficiently laterally to capture and utilize this portion of bone. Thus, poor placement and subsidence of implants can occur leading to implant failure and diseases of the spine such as kyphosis (e.g., a curvature of the upper spine which can be either the result of bad posture or a structural anomaly in the spine), lordosis (e.g., an inward curvature of a portion of the vertebral column) and foraminal stenosis (e.g., narrowing of vertebral foramen). Implant failure can and does lead to catastrophic clinical failure and exceedingly difficult and potentially dangerous spinal revision strategies.
Conventional implants may use one-piece devices to fill the interbody space. The size of the space filled is dictated by multiple factors such as the surrounding soft tissues (e.g., great vessels, ureter, bowel, sympathetic nerves, etc.), aggressiveness of the surgeon performing the surgery, and the type of implant chosen. These implants usually do not violate the vertebral endplate but do not reliably reach the outermost structurally significant area of bone. The devices are routinely placed centrally within the interbody space where they are commonly in contact only with the softest portion of bone, not the more structurally sound outer cortical apophyseal bone.
Various insertable implants are available in different shapes and configurations. An example of such insertable implants is an expandable cage, which often has treads, which are teeth of spikes that engage the vertebral endplates. Usually, these cages can be screwed or inserted into the interbody via distraction tools only in the cephalocaudal direction (e.g., anteroposterior direction). Cages also require destruction of the vertebral endplate by tapping or cutting the structural bone, thus leading to a greater rate on implant subsidence and foraminal stenosis. Accordingly, there remains a need for a new modular lateral expansion device for placing between vertebral bodies within the vertebral body both in lateral and cephalocaudal directions for enhanced structural support of the spine.